WIP: Move webhooks to API
Get rid of sensor container_service and in memory trigger dispatcher
Refactor TriggerDispatcher to st2common for use in st2api
Dispatch triggers from webhook API controller to message queue
Refactor TriggerWatcher to st2common so it can be used in st2api
WebhookController now watches triggers for webhooks
Remove generic webhook sensor
Check-in moved files
Pass request headers as part of payload
Trigger can also be object for parametrized triggers
Fix webhook to use trigger object for dispatch
Rename trigger queue to trigger_instances_queue for clarity
Routing key must be a string
Rename TriggerPublisher to TriggerInstancePublisher for clarity
Add tests for webhook controller
Merge pull request #811 from StackStorm/webhooks_to_api

WIP: Move webhooks to API